Chicago Bears quarterback Mitchell Trubisky put up a Total QBR of 38.0 through the first three weeks of the season, which ranked 25th in the league. He averaged only 5.7 yards per attempt, which ranked 26th. And he left multiple plays on the field, struggling with deep-ball accuracy in new coach Matt Nagy's offensive system.

That all changed in Week 4, when the second-year pro put up his best NFL game yet, racking up six touchdown passes, 407 total yards and a Total QBR of 98.2 in a blowout of the Bucs.

Let's look at the big picture from Trubisky (and Nagy) through four games, from the positive signs for the 3-1 Bears to the areas of development that still need to be addressed. Can the offense do enough to help one of the league's most improved defenses? If so, this is a playoff team. Here's what I've seen on film:

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